In-situ thin film based temperature sensing for high temperature uniformity and high rate of temperature change thermal reference sources

ABSTRACT

A thin-film device for generating a blackbody spectrum is disclosed. The device includes first layer configured to generate heat in response to an applied voltage and a second layer configured to generate the blackbody radiation spectrum in response to the heat from the first layer. A thermocouple is disposed between the first layer and the second layer for measuring a temperature at the second layer. The thermocouple measures temperature at the second layer in order to control temperature at the second layer. The thermocouple can be a copper-carbon nanotube thermocouple.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of U.S. patentapplication Ser. No. 14/884,459 filed on Oct. 15, 2015, the contents ofwhich are incorporated by reference herein in their entirety.

BACKGROUND

The present disclosure relates to thin-film devices for generating aradiation spectrum and, in particular, to a method and apparatus formeasuring a temperature corresponding to the radiation spectrum at thethin-film device.

In various optical systems, an optical signal is received from an objectat an optical sensor and measurements of the optical signal are obtainedat the optical sensor to determine a property of the object. In order toobtain accurate measurements, it is often necessary to calibrate theoptical sensor using a known photon flux at one or more standardwavelengths. One method for providing a photon flux at a standardwavelength includes heating one or more blackbody radiators to selectedtemperatures and using an optical filter to select a calibrationwavelength. However, the use of traditional blackbody sources tocalibrate an optical sensor introduces size, weight, and power (SWaP)challenges. Thin film devices have been used to create blackbodyradiation spectra while overcoming these challenges. These thin-filmdevices tend to have extended radiative surfaces, such as 10 centimeters(cm) by 10 cm. Effective calibration requires a temperature profilealong the radiative surface that is uniform to within about 0.5 degreeskelvin. Therefore, it is desirable to measure temperature at theradiative surface. However, temperature sensors tend to alter localtemperatures due to their thermal mass and conductivity, therebyaffecting temperature uniformity across the radiative surface. Thepresent disclosure provides a method and apparatus for measuringtemperature of a thin-film blackbody source without substantiallyaffecting the uniformity of the temperature at the radiative surface.

SUMMARY

According to one embodiment of the present disclosure, a thin-filmdevice for generating a blackbody spectrum is disclosed, the deviceincluding: a first layer configured to generate heat in response to anapplied voltage; a second layer configured to generate the blackbodyradiation spectrum in response to the heat from the first layer; and athermocouple between the first layer and the second layer for measuringa temperature at the second layer.

According to another embodiment of the present disclosure, a method forgenerating a blackbody radiation spectrum is disclosed, the methodincluding: providing a thin-film device having a first layer of materialconfigured to generate heat in response to an applied voltage, a secondlayer of material configured to generate the blackbody radiationspectrum in response to the heat from the first layer, and athermocouple between the first layer and the second layer for measuringa temperature at the second layer; supplying a current through the firstlayer to generate heat in the first layer; using the thermocouple layerto measure the temperature at the second layer; and controlling thecurrent at the first layer to provide a selected temperature of thesecond layer for generating the blackbody radiation spectrum.

According to yet another embodiment, a device for measuring atemperature is disclosed, the device including: a thin film layer ofcarbon nanotube material including a main body for disposition at afirst location having a first temperature and a carbon nanotube tailextending from the main body, wherein an end of the carbon nanotube taildistal from the main body is disposed at a second location having asecond temperature to form a reference junction; and an electrode havinga junction end coupled to the main body of the carbon nanotube materialand a contact end away from the main body of the carbon nanotubematerial.

Additional features and advantages are realized through the techniquesof the present disclosure. Other embodiments and aspects of thedisclosure are described in detail herein and are considered a part ofthe claimed disclosure. For a better understanding of the disclosurewith the advantages and the features, refer to the description and tothe drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The subject matter which is regarded as the disclosure is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The forgoing and other features, and advantages ofthe disclosure are apparent from the following detailed descriptiontaken in conjunction with the accompanying drawings in which:

FIG. 1 shows an illustrative optical system for calibrating an opticalsensor in one embodiment of the present disclosure;

FIG. 2 shows a perspective view of an exemplary thin film device of thepresent disclosure in one embodiment;

FIG. 3 shows a side view of a top portion of the exemplary thin filmdevice of FIG. 2;

FIG. 4 shows a side view of a top portion of the thin-film device in analternate embodiment;

FIG. 5 shows a side view of a top portion of the thin-film device in analternate embodiment;

FIG. 6 shows an exemplary thermocouple forming a thermocouple layer ofthe thin-film device in one embodiment of the invention;

FIG. 7 shows a graph of temperature at the second layer and appliedpower from the power supply;

FIG. 8 shows an alumel-chromel thermocouple in another embodiment of thepresent disclosure;

FIG. 9 shows a graph of temperature error versus temperature foralumel-chromel thermocouples having various cross-sectional widths.

DETAILED DESCRIPTION

FIG. 1 shows an illustrative optical system 100 for calibrating anoptical sensor 102, such as an optical sensor or optical detector, inone embodiment of the present disclosure. The optical system 100includes a thin-film device 104 that can be moved into and out of a lineof sight 106 of the sensor 102. The thin-film device 104 provides lightto the sensor 102 in the form of a blackbody radiation spectrum. Thethin-film device 104 has a radiative surface 110 which is oriented toface toward the optical sensor 102. The radiative surface 110 is heatedto a uniform temperature, thereby producing the blackbody radiation atthe radiation surface 110. A filter 108 can be placed between thethin-film device 104 and the optical sensor 102 to allow a photon fluxwithin a selected wavelength window to reach the optical sensor 102. Theselected wavelength window generally corresponds to a calibrationwavelength which is used to calibrate the optical sensor 102.

A power supply 112 supplies a current to the thin-film device 104 toheat the radiative surface 110 to the selected temperature. Athermocouple 114 is coupled to the radiative surface 110 in order tomeasure a temperature at the radiative surface 110. In an exemplaryembodiment, the thermocouple 114 measures the temperature at a locationas close to the radiative surface 110 as possible.

The optical system 100 includes a controller 120 for controlling variousoperations of the radiation source 104. The controller 120 includes aprocessor 122 and a memory storage device 124. In various embodiments,the memory storage device 124 includes a non-transitory memory storagedevice such as a solid-state memory storage device. A set of programs126 may be stored in the memory storage device 124 that, when accessedby the processor 122, implement a method for controlling the radiativesource 104. In one aspect, the controller 120 receives a temperaturemeasurement from the thermocouple 114 and alters an amount of currentsupplied by the power source 112 to the radiation source based on thetemperature measurement.

FIG. 2 shows a perspective view of an exemplary thin film device 104 ofthe present disclosure in one embodiment. The thin-film device 104includes a first layer 202 (also referred to herein as a “first carbonnanotube layer 202”) having electrodes 204 a, 204 b at opposite ends ofthe first carbon nanotube layer 202. The electrodes 204 a and 204 b maybe connected to a power supply (such as power supply 112 of FIG. 1) inorder to supply a current that passes through the first carbon nanotubelayer 202. A coordinate system 225 is provided in FIG. 2 forillustrative and explanatory purposes. The first carbon nanotube layer202, as well as the other layers of the thin-film device 200, isconsidered to lie in the x-y plane of the coordinate system 225. Thecoordinate system 225 defines a top side or face of the thin-filmstructure 200 and a bottom side or face of the thin-film structure 200.For any given layer, the top side generally refers to the region in apositive z-direction with respect to the layer and the bottom sidegenerally refers to the region in a negative z-direction with respect tothe layer. The z-axis defines a longitudinal direction of the thin-filmdevices, while the plane perpendicular to the z-axis may be consideredto be transverse to the longitudinal direction.

The first carbon nanotube layer 202 includes carbon nanotubes that areoriented in the plane of the first carbon nanotube layer 202. A thermalspreading layer 206 is disposed on the top face 202 a of the firstcarbon nanotube layer 202. The thermal spreading layer 206 spreads heattransversely through the x-y plane as the heat travels along the z-axisfrom the first carbon nanotube layer 202. A thermocouple layer 230 isdisposed on a top face of the thermal spreading layer 206. A secondlayer 208 (also referred to herein as a “second carbon nanotube layer208”) is adjoined to the thermocouple layer 230 so that the thermocouplelayer 230 and the thermal spreading layer 206 are sandwiched between thefirst carbon nanotube layer 202 and the second carbon nanotube layer208. The second carbon nanotube layer 208 includes a planar surface 214that extends in the x-y plane and a plurality of carbon nanotubes 216attached to a top of the planar surface 214 and oriented with theirlongitudinal axes aligned normal to the planar surface (i.e., orientedin the z-direction). In one embodiment, the planar surface 214 is alayer of alumina substrate (Al₂O₃). The second layer 208 forms theradiative surface 110 of FIG. 1.

When voltage is applied to the first carbon nanotube layer 202, heat isgenerated which flows out of either a top face 202 a of the first carbonnanotube layer 202 or a bottom face 202 b of the first carbon nanotubelayer 202. The heat flowing from the top face 202 a is transmittedthrough the thermal spreading layer 206 and the thermocouple layer 230to reach the second carbon nanotube layer 208. At the second carbonnanotube layer 208, the heat excites photons from the plurality ofcarbon nanotubes 216, which photons are emitted in the positivez-direction to generate a blackbody radiation spectrum.

The spatial distribution of heat generated by the first layer 202 tendsto vary within the x-y plane. As the heat travels in the +z direction,the thermal spreading layer 206 reduces this variation of heat withinthe x-y plane so that by the time the heat reaches the second carbonnanotube layer 208, the heat is evenly distributed across the surface ofthe second carbon nanotube layer 208. The structure of the thermalspreading layer 206 is selected so as to reduce variation of heat in thex-y direction.

In one embodiment, the thermal spreading layer 206 includes a pluralityof thermally conductive layers for spreading the heat transverselythroughout the x-y plane, producing an even distribution of heat in thex-y plane. In one embodiment, the thermally conductive layers includegraphene sheets. A graphene sheet is a highly thermally anisotropicmaterial and is effective in spreading the heat transversely in the x-yplane. In one embodiment, the thermal spreading layer 206 includes atleast a first graphene sheet 210 a and a second graphene sheet 210 b andcorresponding adhesive layers 212 a-212 c. While two graphene sheets areshown in FIG. 2, it is understood that any number of graphene sheets maybe included in the thermal spreading layer 206. The adhesive layers 212a-212 c are thermally insulating, although not necessarily thermallyanisotropic, and allows for heat transfer along the z-axis. The firstgraphene sheet 210 a is joined to the first layer 202 via a firstadhesive layer 212 a. The second graphene sheet 210 b and the firstgraphene sheet 201 a are joined by adhesive layer 212 b. The secondgraphene sheet 201 b is joined to the thermocouple layer 208 viaadhesive layer 212 c.

The thin-film structure 200 further includes a reflector 220 disposed onthe bottom face 202 b of the first carbon nanotube layer 202. Thereflector 220 is a metal layer that has low heat emittance so that verylittle heat escapes by radiation on the back side of the thin-filmstructure 200. In one embodiment, a graphene sheet 222 and adhesivelayer 224 may be disposed between the first carbon nanotube layer 202and the reflector 220.

FIG. 3 shows a side view of a top portion of the exemplary thin filmdevice 104 of FIG. 2, showing layers between the first layer 202 and thesecond layer 204. A first graphene sheet 304 a is coupled to a topsurface of the first layer 202 via an adhesive layer 306 a. A secondgraphene sheet 304 b is coupled to a top surface of the first graphenesheet 304 a via adhesive layer 306 b. The thermocouple layer 308 iscoupled to the second graphene sheet 304 b via adhesive layer 306 c. Thesecond layer 204 is coupled to the thermocouple layer 308 via adhesivelayer 306 d.

The second carbon nanotube layer 204 includes a thin surface 310(generally an alumina surface) and plurality of carbon nanotubes 312a-312 m oriented so that the longitudinal axes of the plurality ofcarbon nanotubes 312 a-312 m are oriented substantially normal to theplanar surface of the thin alumina surface 310. In general, photonsexcited at the second carbon nanotube layer 204 are emitted into thehalf-space above the second carbon nanotube layer 204, as indicated byemission arrow 315. In various embodiments, the temperature at thesecond carbon nanotube layer 204 has a spatial variation of less than1.0 Kelvin across the surface of the second carbon nanotube layer 204.In another embodiment, the spatial variation is less than 0.5 Kelvin. Inyet another embodiment, the spatial variation is less than 0.1 Kelvin.Thus, each of the plurality of carbon nanotubes 312 a-312 m at thesecond carbon nanotube layer 306 receives substantially a same amount ofheat from the alumina surface 310.

FIG. 4 shows a side view of a top portion of the thin-film device 104 inan alternate embodiment. The first graphene sheet 304 a is coupled to atop surface of the first layer 202 via an adhesive layer 306 a. A secondgraphene sheet 304 b is coupled to a top surface of the first graphenesheet 304 a via adhesive layer 306 b. The thermocouple layer 308 iscoupled to the second graphene sheet 304 b via adhesive layer 306 c. Thethermocouple layer 308 is in direct contact with the second layer 204(i.e., without an intervening adhesive layer).

FIG. 5 shows a side view of a top portion of the thin-film device 104 inan alternate embodiment. The first graphene sheet 304 a is coupled to atop surface of the first layer 202 via an adhesive layer 306 a. Thethermocouple layer 308 is coupled to the first graphene sheet 304 a viaadhesive layer 306 b. The second layer 208 is coupled to thethermocouple layer 308 via the adhesive layer 306 c.

FIG. 6 shows an exemplary thermocouple 600 forming a thermocouple layerof the thin-film device 104 in one embodiment of the invention. Theexemplary thermocouple 600 includes a thin film layer having x- andy-dimensions the same as the x- and y-dimensions of the other layers ofthe thin-film electrode so as to be integrated as a layer of thethin-film device 104. In one embodiment, the main body 604 borders or isadjacent to the second layer 208. The thermocouple 600 is generally athin sheet having a thickness of a few mils so as to cause few or nospatial temperature differences at the second layer 208. In oneembodiment, the width of the thermocouple 600 is about 1.5 mils.

The illustrative thermocouple 600 is a copper-CNT thermocouple. Thecopper-CNT thermocouple includes a carbon nanotube thin film 602 havinga main body 604 and a CNT tail 606. The main body 604 has a length andwidth (x- and y-directions) that is the same length and width as theother layers of the thin-film device 104. The CNT tail 606 forms a stripof material that extends away from the main body 604. A copper electrodeis attached to the CNT tail 606 at a location away from the main body604, thereby forming a reference junction 608. A copper electrode 610 isattached to the main body 604 at a selected location. The thickness ofthe electrode 610 is about 1 mil and its cross-sectional area is small.Thus, the electrode 610 has little thermal mass so as not to disrupt thetransverse temperature uniformity at the second layer. The copperelectrode 610 includes a junction end 612 and a contact end 614 that isdistal from the junction end 612. The junction end 612 is affixed to themain body 604. In one embodiment, the junction end 612 is affixed to themain body 604 via electroless deposition. The distal end of the CNT tail606 (i.e., reference end 608) and the contact end 614 of the copperelectrode 610 are substantially at ambient or room temperature.Meanwhile, the main body 604 of the CNT and the junction end 612 of thecopper electrode 610 are at a temperature of the second layer 208 of thethin-film device 104. In various embodiments, the copper electrode 610and the contact end 614 can be thermally and electrically insulated viaan insulating material 620.

Temperature measurements can be obtained by placing a voltmeter 625across the contact end 614 of the copper electrode 610 and the distalreference junction 608 of the CNT tail 606. Voltage measurements can besent to the control system (120, FIG. 1) which can then raise or lowerthe temperature of the second layer by either increasing or decreasing,respectively, a current through the thin-film device (104, FIG. 1). Inone embodiment, the control system (120, FIG. 1) compares thetemperature measurement to a selected or desired temperature and altersthe current accordingly.

In one embodiment, a single copper electrode 610 is attached to the mainbody 604. However, any number of copper electrodes may be attached tothe main body in various embodiments. As shown in FIG. 6, four copperelectrodes 610, 616, 618, 620 are attached to the main body 604. Thelocations of the copper electrodes 610, 616, 618, 620 can be selected inorder to obtain a temperature profile at various points across a surfaceof the second layer 208. The temperature at each point is monitoredrelative to the common reference junction 606.

FIG. 7 shows a graph 700 of temperature at the second layer 208 andapplied power from the power supply 112. The graph 700 shows data pointsfrom each of the electrodes 610, 616, 618, 620 (listed on the graph asblue, brown orange and green respectively) of FIG. 6. A best-fit line702 is drawn through the data points. Good agreement is seen between theoverlapping temperature measurements at the various electrode contactlocations.

FIG. 8 shows an alumel-chromel thermocouple 800 in another embodiment ofthe present disclosure. The alumel-chromel thermocouple 800 may beformed via vapor deposition, usually in a vacuum, of alumel and chromelon the alumina substrate layer 214 of the second carbon layer 208. Vapordeposition and/or electroplating with masking allows good control ofelectrode width and thickness. The layers of alumel and chromel are fromabout 1 to 3 mils in thickness. In one embodiment, the layers of alumeland chromel are from 1 mil in width, however other widths may be used asdiscussed below with respect to FIG. 9. The small width of the layerscontributes very little thermal mass and therefore provides very littledisruption of the temperature uniformity required at the second layer. Athin strip of alumel 801 is formed at one location while a thin strip ofchromel 803 is formed at another location. In region 805, the alumel 801and the chromel 803 overlap to form a junction. Thermocouple 800 isdescribed as an alumel-chromel thermocouple for illustrative purposesonly and not as a limitation of the invention. In other embodiments, thethermocouple can be made of depositing other suitable metal alloys onthe alumina substrate layer 214 (i.e. Fe:Constantan, Cu:Constantan).

FIG. 9 shows a graph 900 of temperature error versus temperature foralumel-chromel thermocouples having various cross-sectional widths. Theordinate axis displays a difference between the reference temperatureand a sample temperature measured by the thermocouple, while theabscissa shows reference temperatures. The thermocouples have widthsfrom about 10 mils to about 125 mils. Reference temperatures were about25° C., 30° C., 40° C., 50° C., 75° C., 100° C., 125° C. and 150° C. Thegraph 900 shows that the thermocouples at the various widths provide agood reading of the reference temperature to within about 1 degree K andin most instances within about 0.5 degree K. Although this implies that“large” width thermocouples may be used, it may still be desired to usethermocouples having smaller widths.

Therefore, in one aspect a thin-film device for generating a blackbodyspectrum is disclosed, the device including: a first layer configured togenerate heat in response to an applied voltage; a second layerconfigured to generate the blackbody radiation spectrum in response tothe heat from the first layer; and a thermocouple between the firstlayer and the second layer for measuring a temperature at the secondlayer. In one embodiment, the thermocouple further includes acopper-carbon nanotube thermocouple layer. The copper-carbon nanotubethermocouple layer can include a carbon nanotube material having a mainbody proximate the second layer and a carbon nanotube tail and a copperelectrode having a junction end affixed to the main body of the carbonnanotube material and a contact end distal from the main body of thecarbon nanotube material. In one embodiment, the copper electrodeincludes a plurality of copper electrodes and each copper electrodeincludes a junction end affixed to the main body of the carbon nanotubematerial and a contact end distal from the main body of the carbonnanotube material, wherein the thermocouples measure temperatures atvarious locations of the second layer. In another embodiment, thethermocouple layer includes a strip of alumel deposited on the secondlayer and a strip of chromel deposited on the second layer and one endof the strip of alumel is in contact one end of the strip of chromel. Invarious embodiments, the thermocouple produces a local variation of thetemperature at the second layer of less than about +−0.1 kelvin. Athermal spreading layer may be located between the first layer and thesecond layer so that the thermocouple is between the thermal spreadinglayer and the second layer. A voltmeter may be used to measure a voltagedifference across the thermocouple to determine the temperature at thesecond layer. A controller may be used to control a current through thefirst layer in response to the determined temperature.

In another aspect, a method for generating a blackbody radiationspectrum is disclosed, the method including: providing a thin-filmdevice having a first layer of material configured to generate heat inresponse to an applied voltage, a second layer of material configured togenerate the blackbody radiation spectrum in response to the heat fromthe first layer, and a thermocouple between the first layer and thesecond layer for measuring a temperature at the second layer; supplyinga current through the first layer to generate heat in the first layer;using the thermocouple layer to measure the temperature at the secondlayer; and controlling the current at the first layer to provide aselected temperature of the second layer for generating the blackbodyradiation spectrum. In one embodiment, the thermocouple includes acopper-carbon nanotube thermocouple. The copper-carbon nanotubethermocouple includes carbon nanotube material forming a main bodyproximate the second layer and a carbon nanotube tail having anreference junction distal from the second layer and includes a copperelectrode having a junction end affixed to the main body a contact enddistal from the main body, and the temperature is related to a voltagedifference between the reference junction of the carbon nanotube tailand the contact end of the copper electrode. In another embodiment, thethermocouple includes a strip of alumel deposited on the second layerand a strip of chromel deposited on the second layer, wherein an end ofthe strip of alumel is in contact with an end of the strip of chromel.The thermocouple is may be used to measure the temperature at the secondlayer while providing a local variation of the temperature at the secondlayer of less than about +−0.5 kelvin. In one embodiment, the secondlayer includes a planar surface and a plurality of carbon nanotubes,wherein a selected carbon nanotube has a longitudinal axis directedsubstantially normal to the planar surface and emits photons directedalong the longitudinal axis in response to the heat from the firstlayer. A graphene stack may be used to spread the heat from the firstlayer transversely between the first layer and the thermocouple.

In yet another embodiment, a device for measuring a temperature isdisclosed, the device including: a thin film layer of carbon nanotubematerial including a main body for disposition at a first locationhaving a first temperature and a carbon nanotube tail extending from themain body, wherein an end of the carbon nanotube tail distal from themain body is disposed at a second location having a second temperatureto form a reference junction; and an electrode having a junction endcoupled to the main body of the carbon nanotube material and a contactend away from the main body of the carbon nanotube material. Atemperature measurement is obtained at a coupling location of thejunction end of the electrode and the main body of the carbon nanotubematerial. The electrode may include a plurality of electrodes, eachhaving a junction end coupled to the main body of the carbon nanotubematerial and a contact end distal away from the main body. In oneembodiment a width of the electrode is less than about 1 mil. Theelectrode may be affixed to the main body by either electricaldeposition or electroless deposition.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of onemore other features, integers, steps, operations, element components,and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present invention has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the invention. Theembodiment was chosen and described in order to best explain theprinciples of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention forexemplary embodiments with various modifications as are suited to theparticular use contemplated.

While the exemplary embodiment to the invention had been described, itwill be understood that those skilled in the art, both now and in thefuture, may make various improvements and enhancements which fall withinthe scope of the claims which follow. These claims should be construedto maintain the proper protection for the invention first described.

What is claimed is:
 1. A method for generating a blackbody radiationspectrum, comprising: providing a thin-film device having a first carbonnanotube layer configured to generate heat in response to an appliedvoltage, a second carbon nanotube layer configured to generate theblackbody radiation spectrum in response to the heat from the firstcarbon nanotube layer, and a thermocouple between the first carbonnanotube layer and the second carbon nanotube layer for measuring atemperature at the second carbon nanotube layer; supplying a currentthrough the first carbon nanotube layer to generate heat in the firstcarbon nanotube layer; using the thermocouple layer to measure thetemperature at the second carbon nanotube layer; and controlling thecurrent at the first carbon nanotube layer to provide a selectedtemperature of the second carbon nanotube layer for generating theblackbody radiation spectrum.
 2. The method of claim 1, wherein thethermocouple further comprises a copper-carbon nanotube thermocouple. 3.The method of claim 2, wherein the copper-carbon nanotube thermocoupleincludes carbon nanotube material forming a main body proximate thesecond carbon nanotube layer and a carbon nanotube tail having anreference junction distal from the second carbon nanotube layer andincludes a copper electrode having a junction end affixed to the mainbody a contact end distal from the main body, and the temperature isrelated to a voltage difference between the reference junction of thecarbon nanotube tail and the contact end of the copper electrode.
 4. Themethod of claim 1, wherein the thermocouple includes a strip of alumeldeposited on the second carbon nanotube layer and a strip of chromeldeposited on the second carbon nanotube layer and an end of the strip ofalumel is in contact with an end of the strip of chromel.
 5. The methodof claim 1, wherein the thermocouple is further configured to measurethe temperature at the second carbon nanotube layer while providing alocal variation of the temperature at the second carbon nanotube layerof less than about +−0.5 kelvin.
 6. The method of claim 1, wherein thesecond carbon nanotube layer includes a planar surface and a pluralityof carbon nanotubes, wherein a selected carbon nanotube has alongitudinal axis directed substantially normal to the planar surfaceand emits photons directed along the longitudinal axis in response tothe heat from the first carbon nanotube layer.
 7. The method of claim 1,further comprising spreading the heat from the first carbon nanotubelayer transversely using a graphene stack between the first carbonnanotube layer and the thermocouple.